Connected devices are proliferating at an exponential rate. They are not only used for communications between people but are now used increasingly in various situations for communicating information relating to machinery. Thus there are now in operation many communication devices that are connected to each other, for example via one or networks which may be wired, or wireless or both. Examples of such devices include “machine to machine” or “M2M” devices or units. These may be defined as devices that are able to communicate with other devices of similar ability using wired and/or wireless technology. An example of another device of similar ability is a server. Thus for example it is typical for an M2M device to communicate with a server dedicated to an application running on the device. M2M devices have been proposed for use in situations such as smart metering, for example for use of electricity, monitoring the operation of vehicles and many others. The communication of M2M devices with each other and with other devices such as dedicated servers without human intervention has led to the coining of the expression “the internet of things”. It is estimated that the number of communication devices including M2Ms and those for personal use, already exceeds the number of humans on earth. This proliferation can lead to problems for network operators, particularly cellular network operators, as will be explained in more detail below.